The silicon photodiode used in a solid state imaging device has sensitivity not only in the visible region, but also up to the near infrared. Therefore, as for a seal glass, it is ordinary to use a glass to which a near infrared cut function is given in order to cut a near infrared.
However, because such the glass having a near infrared cut function is expensive, it has been desired to develop a liquid composition having such the near infrared cut function, and moreover to develop a thermosetting or photo-setting composition.
When a liquid composition is marketed, the liquid composition is handled like a color filter. Therefore, both heat resistance and light fastness different from a glass are required. However, conventional near infrared cut materials are not sufficient for heat resistance and light fastness. Resultantly, there is no liquid composition of the practical use level on the market because of its inferior heat resistance and light fastness.
There are many patent publications relating to the near infrared cut materials including not only inorganic materials, but also organic materials. As the inorganic compound, there are known a Cu-containing resin film having formed a complex of a phosphorus-containing resin and Cu+, described in publications such as JP-A-2001-154015 (“JP-A” means unexamined published Japanese patent application), JP-A-9-184914 and JP-A-8-75919; ytterbium phosphate compounds described in publications such as JP-A-10-49642 and JP-A-10-88107; cupper phosphate described in publications such as JP-A-2004-231708; metal oxides represented by ITO, ATO, Zinc oxide and the like; hexa boride particles described in publications such as JP-A-2004-18295; metal nano rods described in publications such as JP-A-2004-198665 and JP-A-2003-315531; and the like.
As the organic compound, there are known phthalocyanine compounds described in publications such as JP-A-2000-214628, JP-A-2000-26748 and JP-A-11-60579; dimonium compounds described in publications such as JP-A-11-323121; naphthalocyanine compounds described in publications such as JP-A-2000-44883, JP-A-11-60580 and JP-A-11-152415; aminonaphthalocyanine compounds described in publications such as JP-A-11-152416; aminothiophenolate-series metal complex dyes described in publications such as JP-A-11-349920; cyanine dyes and oxonol dyes described in publications such as JP-A-2002-90521; squarylium dyes and croconium dyes described in publications such as JP-A-2002-122729; quinodimethane derivatives described in publications such as JP-A-11-116567; polymethine-series dye compounds described in publications such as JP-A-2000-302992; anthraquinone compounds described in publications such as JP-A-2001-108815; substituted sulfonylbenzenedithiol nickel complexes described in publications such as JP-A-2001-288380; and the like. Almost all of these compounds are known as applications to plasma display. As for applications to the above-described solid state imaging device, however, there is no description of a liquid composition that can be used as a substitute of the seal glass from the viewpoints of heat resistance and light fastness.
In fact, those compounds as described in these patent publications are insufficient for use of the solid state imaging device in terms of heat resistance and light fastness. Further, many of these compounds are difficult to distinguish a visible region from a near infrared region.
In view of these problems, it has been desired to develop a near infrared-absorbing dye-containing liquid composition that has substantially no absorption in the visible region, but in the near infrared region, thereby having ability to cut a needless near infrared light to which a silicon photodiode has sensitivity, and also that is excellent in heat resistance and light fastness. Besides, a further improvement of light fastness has been desired with respect to the near infrared-absorbing filter for a plasma display panel.